The invention relates to an ultrasonic airspeed and direction sensor system and in preferred embodiments relates to such a system for mounting to a vehicle such as an aircraft. Provision of airspeed and direction improves pilot situational awareness and enhances aircraft fatigue monitoring.
One example of a known sensor for use with aircraft is described in U.S. Pat. No. 4,031,756. In this, a base supporting element is mounted to the front of the aircraft such as a helicopter and includes a central arm on which are mounted three transmitting transducers and surrounding the transmitter support are provided three receiver transducer housings incorporating receiving transducers, one of those housings including a further receiver transducer. Ultrasonic signals are transmitted from the transmitting transducers to the receiving transducers along respective paths and the speed and direction of air flow can be determined.
One of the problems with this known sensor is that it has to be made very robust to minimize vibration errors and therefore has large supporting members in order to reduce vibration but this then limits the directions of air flow that can be monitored. Particularly, if the aircraft is moving in a direction a little different from a forward direction, parts of the body of the sensor will occlude air flow resulting in erroneous measurements.